Brentford ran out second-best at London Road with the home side scoring three times without reply, two in a six minutes second half blitz. Martin Allen kept faith with the side that defeated Wrexham, promoting Second Year Scholar Ryan Peters to the subs bench.
Rankin was close to stealing an early lead for the visitors but his shot went wide. Andy Legg's long throw almost led to the opening goal in the eighteenth minute, Clive Platt's off-target header serving the home side's intent. Brentford replied sixty seconds later, Chris Hargreaves deft header from a John Salako cross fizzing just wide of Tyler's left-hand post.
In the 21st minute the opening goal arrived - and like the half before it - in scrappy fashion. Posh striker Andy Clarke released Andy Legg down the left-hand channel. The Welshman's cross was finally dispatched by Clive Platt, despite the Brentford backline's attempts to clear their lines. Brentford's best move of the half came in the 39th minute. Peter Kennedy's brilliant tackle denied the on-rushing Isaiah Rankin a certain goalscoring opportunity.
Supporters from both sides barely has a chance to take their seats before Peterborough doubled their lead, Andy Legg stabbing the ball home from eight yards. If that was bad news, worse was to follow six minutes later, as Andy Clarke kept up his remarkable goalscoring record against Brentford with his side's third; a powerful header past Nelson from a Kennedy cross.
Ryan Peters - celebrating his seventeenth birthday - was given his Brentford debut as substitute, and his second-half display was energetic enough to suggest he will be involved again with the first-team squad.
Line-up: Nelson, Dobson, Frampton, Fitzgerald, Turner, Hargreaves, Talbot (sub O'Connor 60 mins), Tabb (sub Peters 51 mins), Salako (sub Rhodes 55 mins), Rankin, Burton.
Attendance: 4,868 (789 Bees).